Sol-Gel Electroceramic Thin Films

The first studies on sol-gel processing of ceramic materials were performed by Roy and coworkers [2,3] who prepared a large number of compositions, involving Al, Si, Ti, Zr, and so on. These could not be prepared then by using the 

The Sol-Gel Handbook Synthesis, Characterization, and Applications, First Edition. 

Voltage-dependent resistors (varistors) resistance varies with voltage 

Temperature-sensitive resistors (thermistors) resistance varies with temperature 

Fuel cells and batteries use chemical reactor to provide electricity 

---

Figure 27.2 (a) Sol-gel precursor solutions film deposited on a Pt-coated silicon subused for the deposition of thin films, (b) Cross- strate. The spots on the film surface are top Pt sectional SEM image of an electroceramic thin electrodes deposited for the fabrication of film, (c) Photograph of an electroceramic thin capacitors. 

Figure 27.2 shows the photographs of sol-gel precursors and thin films prepared by CSD. This chapter presents a snapshot of the current status and key challenges in the field of electroceramic thin films processed by sol-gel. This chapter is mainly focused on metal oxide films, which are the most lucrative films prepared by CSD with the widest use in electroceramic devices. However, non-oxide materials have also been prepared by sol-gel and detailed overviews on them were reported by Kamiya [5,6], Fujihara [7], and Almeida and Xu [8]. 

The development of sol-gel chemistry for the fabrication of oxide thin films by CSD started first in the 1980s with the deposition of transparent coatings of silica layers [9,10]. Immediately after these works, the CSD preparation of crystalline complex oxide thin films was reported, first by Fukushima [11] for BaTiOs films and a year later by Budd et al. [12] for PbTiOs and PbZrOs films. Since then, CSD has been widely used for the preparation of electroceramic thin films. 

This chapter shows the potential of sol-gel chemistry for the synthesis of solution precursors used in the CSD of thin films with electrical properties. CSD is an alternative low-cost deposition technique to the vacuiun and high-temperature deposition methods that, in addition, makes it possible to obtain stoichiometric and uniform thin films. Electrical properties of electroceramic thin films are extremely sensitive to processing, microstructure, heterostructure, crystallinity, or charged defects of the film. Sol-gel offers the chance of controlling these film characteristics and therefore the functional properties by tailoring the solution chemistry and the thermal conversion of the as-deposited gel layer into a ceramic film. 

Meneses C.T., Macedo M.A., Vicentin F.C. Li Mn204 thin films characterization by X-ray, electrical conductivity and XANES. Microelectronics J. 2003 34 561-563 Mori T, Kawano K., Oda N. High-TCR bolometer thin films by sol-gel processing. Electroceram. Jpn. Ill 2000 181-1 117-120... 

Table 27.1 Main types of electroceramic materials that can be prepared in thin film form from sol-gel precursors/solutions dielectric and insulators, piezoelectrics, pyroelectrics, magnetics, and muitiferroics.

---